A fundamental difference between the display of a digital image on a printer and on a liquid crystal display is that the resolution of the printer may be changed without changing the size of the image, but a change in the resolution of the LCD results in a corresponding change in the height and width of the image, because the size of a picture element (“pixel”) on an LCD is fixed by the circuitry on the display.
There are three important elements involved in the display of a digital image on an LCD panel. The first of these is LCD panel itself. In a flat panel LCD, as to which this application pertains, a substantially rectangular screen area is divided into a large number of individual color dots, each color dot being positioned at an intersection of a row and a column electrode. A set of these color dots comprises a pixel, and the terms “color dot set” and “pixel” should be understood as being equivalent in this specification. Each set of color dots is capable of displaying a full color gamut. There are many combinations of color dot sets, but the most common sets are: a strip of three dots in a three column, one row matrix of red, green and blue color dots, a four-dot combination of red, green, green and blue arranged in a two column, two row matrix; a four-dot combination of red, green, blue and white, also arranged in a two column, two row matrix; and a six-dot combination of red, green, blue, yellow, cyan and magenta, usually arranged in a three column, two row matrix.
In an active matrix flat panel LCD, each color dot contains a transistor switch. A liquid crystal fluid, contained between a front plate and a rear plate, is twisted by a voltage which changes the axis of polarization of light, allowing the individual color dots to either transmit or not transmit light passing from a backlight source through the individual color filters. In the known art, each color dot in a pixel is driven by electrical impulses fed to its row and column address by the electrodes. In the typical embodiment, a gray scale impulse is received along the column electrode and this gray scale impulse sets the degree of twist of the liquid crystal fluid, thereby setting the amount of light allowed to pass from the backlight source through the color filter. The column electrodes are generally referred to as the source channels. The row electrodes, which are generally referred to as the gate channels, provide a timed impulse to a capacitor associated with the transistor of a given color dot, turning it from “off” to “on” for a “line time”. It is during this line time that the gate driver signal determines the voltage that will be held by the color dot transistor for an entire frame period, that is, until the gate driver sends a subsequent signal down the row to refresh the capacitor charge. Since only one row is receiving the gate signal at a time, only one color transistor in a column is receiving a gray scale impulse at a time. By repeatedly scrolling through the rows and delivering gray scale impulses along the columns, a color image is displayed on the LCD.
The second element involved in the digital display is the bus hardware that delivers the row and column impulses in a precisely timed manner to the row and column electrodes. One well known device for delivering such impulses to the electrodes is the so-called tape-actuated bonding, or TAB. These TABs contain integrated circuitry and each one is capable of being connected with a fixed number of rows or columns. TABs come in standard off-the-shelf sizes, the size being primarily set by the number of channels which it may address. Because pixels tend to be either two or three columns wide, TABs tend to have a number of channels that is evenly divisible by six, as such a design allows use with both two- and three-column pixels. Two commonly used TABs have 384 and 480 channels, respectively. Clearly, it is advantageous to attach an integral number of identically-sized TABs along one of the side edges and one of the top and bottom edges, to deliver the respective row and column impulses.
The third, but far from least important, element involved in the display of a digital image is the two-dimensional digital data array that comprises the image itself. Arranged by rows and columns, the digital data array contains a gray scale value for each row and column of a single frame of the image. When the gray scale data for a given pixel on the LCD is delivered along the column electrodes through the appropriate column (source) TAB at the time when the associated row electrode is transmitting an “on” signal to the given pixel through the row (gate) TAB, the result is the digital image contained in the digital data array. The storage and refreshing of the digital data in the digital data array is a known technology that will be familiar to one of ordinary skill in this art without being repeated here.
As may be expected, a specific digital data array may need to be displayed in a variety of different LCDs, so the designer of the LCD, in order to display the full image, selects a panel with a set of source and gate TABs attached thereto, where the number of source channels is larger than the number of columns in the data array and the number of gate channels is larger than the number of rows in the data array. This excess of each type of channel is generally referred to as the number of “dummy” channels. Existing solutions have amassed these dummy channels in a few different configurations. In one solution, the excess dummy channels in each direction are divided into two blocks, with one block placed at the respective ends of the display. This technique places an inactive “frame” area around the active image. In a second solution, all the dummy channels in a direction are placed in a single block at one end of the display, resulting in an “L” shape of inactive area adjacent to the active image.
While it will be easily recognized that existing techniques do not provide an attractive presentation of the image on the LCD, and in fact, does not fully utilize the size dimensions of the panel used.
It is therefore an unsolved need to expand a digital image display generated from a digital data array to fill an available display panel, even when the display panel exceeds, in number of pixels, the size of the digital data array provided, especially by up to a factor of about 20% in at least one dimension of the array.